Arctic vegetation and soil biological communities interact with a range of biotic and abiotic factors to produce or consume the greenhouse gases (GHG) carbon dioxide, methane, and nitrous oxide. In Arctic environments the parameters controlling these processes are not well understood. We measured soil GHG concentrations and surface fluxes from six vegetation communities at a High Arctic polar oasis and adjacent polar deserts in order to identify regions within the soil profile of production and consumption of CO₂, CH₄, and N₂O. Examined communities included two polar deserts differing in parent material and soil pH, and four lowland tundra communities: prostrate dwarf-shrub, herb tundra, prostrate/hemiprostrate dwarf-shrub tundra, nontussock sedge, dwarf-shrub, moss tundra and a sedge/grass, moss wetland, representative of large areas at lower Arctic latitudes. Polar desert soils were net producers of greenhouse gases during the brief High Arctic growing season, including at depths close to the permafrost layer, and effluxes from the surface were of a similar magnitude to nearby mesic and hydric tundra soils including for CO₂, indicative of soil respiration in desert soils with few roots. Differences in water content, rather than calculated diffusivity, appear to drive gas transport in at least some soils, with all three GHG appearing to move rapidly through, for example, the soil at 10 cm above permafrost in the Prostrate (dominated by Dryas integrifolia) plant community. Such physical processes may obscure or falsely suggest biological processes in soil ecosystems.

Production and consumption of greenhouse gases such as CO₂, CH₄ and N₂O are key factors driving climate change. While CO₂ sinks are commonly reported and the mechanisms relatively well understood, N₂O sinks have often been overlooked and the driving factors for these sinks are poorly understood. We examined CO₂, CH₄ and N₂O flux in three High Arctic polar deserts under both light (measured in transparent chambers) and dark (measured in opaque chambers) conditions. We further examined if differences in soil moisture, evapotranspiration, Photosynthetically Active Radiation (PAR), and/or plant communities were driving gas fluxes measured in transparent and opaque chambers at each of our sites. Nitrous oxide sinks were found at all of our sites suggesting that N₂O uptake can occur under extreme polar desert conditions, with relatively low soil moisture, soil temperature and limited soil N. Fluxes of CO₂ and N₂O switched from sources under dark conditions to sinks under light conditions, while CH₄ fluxes at our sites were not affected by light conditions. Neither evapotranspiration nor PAR were significantly correlated with CO₂ or N₂O flux, however, soil moisture was significantly correlated with both gas fluxes. The relationship between soil moisture and N₂O flux was different under light and dark conditions, suggesting that there are other factors, in addition to moisture, driving N₂O sinks. We found significant differences in N₂O and CO₂ flux between plant communities under both light and dark conditions and observed individual communities that shifted between sources and sinks depending on light conditions. Failure of many studies to include plant-mediated N₂O flux, as well as, N₂O soil sinks may account for the currently unbalanced global N₂O budget.

We evaluated above‐ and belowground ecosystem changes in a 16 year, combined fertilization and warming experiment in a High Arctic tundra deciduous shrub heath (Alexandra Fiord, Ellesmere Island, NU, Canada). Soil emissions of the three key greenhouse gases (GHGs) (carbon dioxide, methane, and nitrous oxide) were measured in mid‐July 2009 using soil respiration chambers attached to a FTIR system. Soil chemical and biochemical properties including Q₁₀ values for CO₂, CH₄, and N₂O, Bacteria and Archaea assemblage composition, and the diversity and prevalence of key nitrogen cycling genes including bacterial amoA, crenarchaeal amoA, and nosZ were measured. Warming and fertilization caused strong increases in plant community cover and height but had limited effects on GHG fluxes and no substantial effect on soil chemistry or biochemistry. Similarly, there was a surprising lack of directional shifts in the soil microbial community as a whole or any change at all in microbial functional groups associated with CH₄ consumption or N₂O cycling in any treatment. Thus, it appears that while warming and increased nutrient availability have strongly affected the plant community over the last 16 years, the belowground ecosystem has not yet responded. This resistance of the soil ecosystem has resulted in limited changes in GHG fluxes in response to the experimental treatments.

Background and aims Approximately 50 % of belowground organic carbon is present in the northern permafrost region and due to changes in climate there are concerns that this carbon will be rapidly released to the atmosphere. The release of carbon in arctic soils is thought to be intimately linked to the N cycle through the N cycle’s influence on microbial activity. The majority of new N input into arctic systems occurs through N₂-fixation; therefore, N₂-fixation may be the key driver of greenhouse gases from these ecosystems.
Methods At Alexandra Fjord lowland, Ellesmere Island, Canada concurrent measurements of N₂-fixation, N mineralization and nitrification rates, dissolved organic soil N (DON) and C, inorganic soil N and surface greenhouse gas fluxes (CO₂, N₂O and CH₄) were taken in two ecosystem types (Wet Sedge Meadow and Dryas Heath) over the 2009 growing season (June-August). Using Structural Equation Modelling we evaluated the hypothesis that CO₂, CH₄ and N₂O flux are linked to N₂-fixation via the N cycle.
Results The soil N cycle was linked to CO₂ flux in the Dryas Heath ecosystem via DON concentrations, but there was no link between the soil N cycle and CO₂ flux in the Wet Sedge Meadow. Methane flux was also not linked to the soil N cycle, nor surface soil temperature or moisture in either ecosystem. The soil N cycle was closely linked to N₂O emissions but via nitrification in the Wet Sedge Meadow and inorganic N in the Dryas Heath, indicating the important role of nitrification in net N₂O flux from arctic ecosystems.
Conclusions Our results should be interpreted with caution given the high variability in both the rates of the N cycling processes and greenhouse gas flux found in both ecosystems over the growing season. However, while N₂-fixation and other N cycling processes may play a more limited role in instantaneous CO₂ emissions, these processes clearly play an important role in controlling N₂O emissions.

Polar deserts dominate the High Arctic covering over 1 358 000 km² but little is known about greenhouse gas (GHG) production or flux in polar desert soils. We measured soil-atmosphere GHG exchange for CO₂, CH₄, and N₂O, and net production of these gases in the active layer at 30 sites across three polar deserts in the High Arctic on Ellesmere Island, Canada for a total of 180 production/consumption estimates. There was inter-annual consistency in patterns of GHG net production and a consistent, significant, positive relationship (r² = 0.91–0.93; p < 0.05) between CO₂ production and N₂O production in Arctic desert sites. This differs from the negative correlations found in wet or moist tundra ecosystems and may arise from the large N₂O emissions in dolomitic desert ecosystems. Global change processes that increase microbial activity in deserts will likely increase N₂O emissions but increases in activity in wetter tundra will decrease N₂O emissions. However, given the unusual co-consumption of CH₄ and N₂O in the deserts, it is not clear if models of GHG production developed for other ecosystems will apply to these unique Arctic environments.

New technologies in trace gas detection are revolutionizing our ability to study soil microbiological ecosystems. Field-deployable infrared-spectroscopy detectors capable of rapidly measuring multiple analyte gases simultaneously allow estimates of soil:atmosphere gas exchange and below-ground gas concentrations, and production dynamics across divergent ecosystems, creating opportunities to study interactions between microorganisms, soils, atmospheres, and global cycling, as well as interactions between different gases. The greenhouse gases CO₂, CH₄, and N₂O can be measured in the field and compared to each other to uncover links between the biochemical pathways responsible for the production and consumption of these gases. We have developed techniques using a nondestructive, Fourier-transform infrared detector under remote field conditions in three campaigns in the Canadian High Arctic to measure highly variable gas processes in soils.

There are unusual patterns of greenhouse gas (GHG) net production in soil profiles of Arctic polar deserts. These deserts include frost boils that are symptomatic of permafrost‐associated soils. Some frost boils contain diapirs, intrusions of recently thawed, carbon‐ and water‐rich fine material pushed upward into the overlying active layer. Here we identified diapir‐associated frost boils in an Arctic polar desert that we had previously found to have highly variable patterns of GHG net production, and compared patterns of GHG net production in soil profiles between diapir and non‐diapir frost boils. In addition, we tested the repeatability of soil gas probes measurements and if estimates of diffusivity based on bulk density were accurate. Probes were installed in frost boils identified as including or not including diapirs, and measurements were conducted over several days to evaluate net GHG production.
Soil gas probes deployed for longer than approximately 3 d showed loss of signal, and the injection of an inert tracer, SF₆, validated our estimates of soil diffusivity based on bulk density. Diapir‐associated frost boils showed reduced soil respiration compared with non‐diapir frost boils, despite these diapir‐associated frost boils having increased soil organic matter content. Thus, diapir intrusions in frost boils of the Arctic polar desert simultaneously store greater amounts of organic C and reduce soil respiration compared with non‐diapir frost boils. Differences in soil organic matter quality and/or its interaction with soil texture may be an important control for carbon storage in Arctic soils.